1. Field of the Invention
The present invention relates to an ink suitable for ink jet recording, and an ink cartridge and an ink jet recording method using the ink.
2. Description of the Related Art
In recent years, a pigment ink containing an organic pigment as a coloring material has started to be widely used as a color ink for use in an ink jet recording method for the purposes of additionally improving the fastness properties of an image such as gas resistance and light fastness. In the pigment ink, the organic pigment is dispersed in an aqueous medium by means of, for example, a water-soluble resin as a dispersant, encapsulation with the resin, or the modification of the surface of a pigment particle with the resin. In general, however, an image recorded with the pigment ink involves the following problem. The color developability of the image is insufficient as compared with that in the case of a dye ink. In addition, the following problem arises owing to the fact that the pigment is a particle. The glossiness of each of images recorded on recording media each having a glossy surface (so-called glossy papers) with the pigment ink is particularly insufficient as compared with that in the case of the dye ink. It should be noted that the term “glossiness” as used herein refers to the 20° gloss value of an image, and the image can be regarded as being excellent in glossiness when the 20° gloss value is 50 or more. The value can be measured with, for example, a Microhazemeter (manufactured by BYK-Gardner GmbH).
Various investigations have been heretofore conducted on the above-mentioned problems. With regard to, for example, the color developability of an image, the following pigment ink has been proposed (see Japanese Patent Application Laid-Open No. 2004-238445). Resin fine particles are added to the pigment ink, and a ratio between the particle diameters of a pigment and a resin fine particle is set to fall within such a specific range that the color developability of an image in the so-called plain paper is improved. In addition, with regard to the glossiness of an image, the following ink prescription has been proposed (see Japanese Patent Application Laid-Open No. 2005-194500). A 1,2-alkanediol is added to a pigment ink so that the smoothness of an ink dot in a recording medium may be improved and the glossiness of the image may be improved.